1.
J. Friess1, U. Sonntag, I. Steller, A Bührig-Polaczek
1 Foundry Institute of RWTH Aachen University, Aachen, Germany
2 GFaI – Society for the Advancement of Applied Computer Science, Berlin, Germany
3 BDG – German Foundry Association, Duesseldorf, Germany
DEVELOPMENT OF A UNIFORM ANALYTIC PROCEDURE FOR THE SYSTEM-INDEPENDENT EVALUATION OF GRAPHITE MORPHOLOGY AND NODULARITY OF DUCTILE CAST IRON

2.
Z. Zovko Brodarac1, D. Stanić2, F. Kozina1
1 University of Zagreb Faculty of Metallurgy, Sisak, Croatia
2 CIMOS-P.P.C. Buzet, d.o.o, Buzet, Croatia; Polytechnic Pula - College of applied sciences, Pula, Croatia
INFLUENCE OF Cu ON THE MICROSTRUCTURE DEVELOPMENT OF AlSi7MgCu ALLOY

3.
J. Medved1, S. Kores2, T. Balaško1, M. Vončina1
1University of Ljubljana, Faculty of Natural Sciences and Engineering, Department for Materials and Metallurgy, Ljubljana, Slovenia
2 Talum Tovarna aluminija d. d. Kidričevo, Kidričevo, Slovenia
INFLUENCE OF MINOR ALLOYING ELEMENT ADDITION ON ALUMINIUM CASTING ALLOYS

4.
D. Arnšek1, F. Zupanič1, B. Podgoršek2, T. Bončina1
1University of Maribor, Faculty of Mechanical Engineering, Maribor, Slovenia,
2Omco Metals Slovenia d. o. o., Žalec, Slovenia
DETERMINATION OF MICROSTRUCTURAL CONSTITUENTS IN AN ADVANCED ALUMINIUM BRONZE

DEVELOPMENT OF A UNIFORM ANALYTIC PROCEDURE FOR THE SYSTEM-INDEPENDENT EVALUATION OF GRAPHITE MORPHOLOGY AND NODULARITY OF DUCTILE CAST IRON

Abstract

The quantitative determination of graphite morphologies in spheroidal cast iron plays a major role for quality control and material development. Next to the well-established but subjective comparison method by visual analysis, the digital image analysis is a promising tool to enable an objective and reproducible analyzing method. To date the latter still lacks of a standardized procedure thus causing variations in graphite shape classification as well as nodularity in practice.
In this study various parameters and factors during the entire metallographic procedure were investigated including the steps sample preparation, image acquisition, image processing, measurement, classification and nodularity determination in order to understand the different causes for varying digital image analysis results and thus to develop a uniform analytic procedure for a system-independent evaluation of graphite morphology.
It was demonstrated that camera settings with different calibrations and lighting configurations determine majorly the recorded image data and its accuracy and thus are substantial reasons for variant classification results. Furthermore, differently implemented threshold algorithms for binarizing the image to distinguish graphite from the surrounding iron matrix influence the measured shape of graphite particles. Additionally, in recent standards for nodularity nodules are only defined by roundness above 0.6, whereas a complete classification of graphite shapes sues the combination of different shape parameters like sphericity and solidity next to roundness.

Keywords: ductile iron, image analysis, nodularity, graphite morphology, graphite classification

INFLUENCE OF Cu ON THE MICROSTRUCTURE DEVELOPMENT OF AlSi7MgCu ALLOY

Abstract

Designing and characterisation of AlSi7MgCu alloy with extra addition of Cu (up to 1.435 wt.%) represents a challenge in order to achieve advanced mechanical properties already in as- cast state. Microstructural investigation of AlSi7MgCu alloy reveals a wide range of complex reactions and possible intermetallic phases due to the interaction of alloying and trace elements. An extra addition of Cu (up to 1,435 wt.%) as a secondary alloying element initiates an additional interaction with transition elements Fe, Mn and secondary alloying element Mg. Evolution of microstructure and determination of solidification sequence enables a detailed overview of the solidification path in both states, as-cast and heat-treated. Enrichment of solidification process with complex intermetallic phases reveals the following constituents: dendrite network; iron-based needle-like Al5SiFe and / or complex Chinese script formation Al15(Fe,Mn,Cu)3Si2;maineutectic(αAl+βSi);complexeutecticclustersof Al8Mg3(Fe,Mn,Cu)Si6 and Al5(Fe,Mn,Cu)2Mg8Si6 phase and secondary eutectic phase precipitations αAl+Mg2Si and αAl+Al2(Fe,Mn,Cu). Infiltration of common transition elements such as Fe and Mn in Cu bearing phases resulted in high total content of transition elements (Fe+Mn+Cu). Microstructural investigation also indicates continuous interaction of Fe, Mn and Cu in formation of wide range of intermetallic phases through the whole solidification process.
The nature (morphology and alloying elements interaction) of formed intermetallic phases comprehends to the tensile mechanical properties’ development due to strong connections and interactions during solidification process as a whole.

Keywords: AlSi7MgCu alloy, copper, microstructure, transition elements

INFLUENCE OF MINOR ALLOYING ELEMENT ADDITION ON ALUMINIUM CASTING ALLOYS

Abstract

Standard materials do not satisfy the rigorous requirements for complex applications. The paper represents the modeling of innovative aluminium alloys with better properties for high temperature applications. Thermodynamic equilibrium calculations, simple thermal analysis and differential scanning calorimetry were used in order to analyse the influence of joint micro- addition of zirconium and molybdenum on solidification of Al-Si-Mg-Mn alloy, whereas the optical microscopy and scanning electron microscopy as well as the energy dispersive spectroscopy were employed to investigate the microstructure development of investigated experimental alloys.
An analysis of chemical composition and types of phases, the amount of phase and study of equilibrium and non-equilibrium processes and the characteristic solidification temperatures for laboratory and industrial aluminium alloys were made. When zirconium was added to the alloy, a needle-like phase formed. Molybdenum in the alloy is incorporated into the AlFeMnSi phase, and in some cases completely replaced iron, and formed a new AlFeMnMoSi phase with a different morphology in a more roundish Chinese script.

Keywords: Aluminium casting alloys, Minor alloying addition, Thermodynamics, Solidification, Microstructure

4.
D. Arnšek1, F. Zupanič1, B. Podgoršek2, T. Bončina1
1University of Maribor, Faculty of Mechanical Engineering, Maribor, Slovenia,
2Omco Metals Slovenia d. o. o., Žalec, Slovenia

DETERMINATION OF MICROSTRUCTURAL CONSTITUENTS IN AN ADVANCED ALUMINIUM BRONZE

Abstract

In this investigation, we investigated a sand-cast aluminium bronze containing 18 % Ni. The bronze was sand cast. The analyses were carried out on cast-on tensile specimens. The samples were prepared by appropriate metallographic methods. They were investigated using light microscopy, scanning electron microscopy, microchemical analysis, X-ray diffraction and differential thermal analysis.

A typical as-cast microstructure consists of globular β phase, which is fact the intermetallic phase AlNi. There are two types of two-phase constituents in the interdendritic spaces; both comprising of α-Cu (Cu-rich solid solution) and β. In the first (α-Cu + β-AlNI) constituent, there are coarse β-rods in phase α, while the second (α-Cu + β-AlNi) constituent exhibits a lamellar (α-Cu + β-AlNi) structure. Also, iron-chromium borides are present in the microstructure. The microstructure of the DTA-sample is qualitatively the same, but the microstructural constituents are considerably coarser.

Keywords: aluminium bronze, nickel, microstructure, solidification